NEET Sample Paper NEET Sample Test Paper-48

  • question_answer
    An asteroid of mass m is approaching earth, initially at a distance of \[10{{R}_{e}} with speed {{V}_{1}}.\] It hits the earth with a speed V (R and M radius and mass of earth), then:

    A) \[{{\operatorname{V}}^{2}}_{f}={{V}_{1}}^{2}+\frac{2GM}{{{M}_{e}}R}\left[ 1-\frac{1}{10} \right]\]

    B) \[{{\operatorname{V}}^{2}}_{f}={{V}_{1}}^{2}+\frac{2GM}{{{R}_{e}}}\left[ 1+\frac{1}{10} \right]\]

    C) \[{{\operatorname{V}}^{2}}_{f}={{V}_{1}}^{2}+\frac{2GMe}{{{R}_{e}}}\left[ 1-\frac{1}{10} \right]\]

    D) \[{{\operatorname{V}}^{2}}_{f}={{V}_{1}}^{2}+\frac{2GM}{{{R}_{e}}}\left[ 1-\frac{1}{10} \right]\]

    Correct Answer: C

    Solution :

    \[\operatorname{Kinetic} energy of asteroid =\frac{1}{2}m{{v}^{2}}\] \[\operatorname{P}.E of asteroid =\frac{-GMm}{10{{R}_{e}}}\] Apply law of energy conservation \[{{\operatorname{K}}_{1}}+{{P}_{1}}={{K}_{2}}+{{P}_{2}}\] \[\frac{1}{2}m{{v}_{1}}^{2}-\frac{GMm}{10{{R}_{e}}}+\frac{1}{2}{{\operatorname{mv}}_{\operatorname{f}}}^{2}-\frac{GMm}{{{R}_{e}}}\] \[\frac{{{v}_{1}}^{2}}{2}-\frac{GM}{10{{R}_{e}}}+\frac{GM}{{{R}_{e}}}=\frac{{{v}_{\operatorname{f}}}^{2}}{2}\] \[{{v}_{\operatorname{f}}}^{2}={{v}_{1}}^{2}+\frac{2GM}{{{R}_{e}}}\left[ 1-\frac{1}{10} \right]\]


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